# Find the magnitude of acceleration of the puck on the ramp

## Homework Statement

A .20 kg hockey puck is launched up a metal ramp that is inclined at a 30.0 degree angle. The coefficients of static and kinetic friction between the hockey puck and the metal ramp are
Ms= .40 kg and Mk=.30 kg , respectively. The puck's initial speed is 35.0 m/s. What is the magnitude of the acceleration of the puck on the ramp?

F= ma

## The Attempt at a Solution

N= Nj
Fgrav= mg(cos 30- sin 30)
Friction= MkN

In the j direction the forces are:
N-mgsin(30)=0
N= -1.94
In the i direction the forces are:
mgcos(30) + MkN=ma
a= (mgcos(30)+ MkN)/ m =a

then when I plug in all of the given numbers I get -1.4.
I have tried this problem a bunch of times and cannot get anywhere close to the correct answer. What am I doing wrong?

PhanthomJay
Homework Helper
Gold Member

## Homework Statement

A .20 kg hockey puck is launched up a metal ramp that is inclined at a 30.0 degree angle. The coefficients of static and kinetic friction between the hockey puck and the metal ramp are
Ms= .40 kg and Mk=.30 kg , respectively. The puck's initial speed is 35.0 m/s. What is the magnitude of the acceleration of the puck on the ramp?

F= ma

## The Attempt at a Solution

N= Nj
Fgrav= mg(cos 30- sin 30)
Friction= MkN

In the j direction the forces are:
N-mgsin(30)=0
N= -1.94
In the i direction the forces are:
mgcos(30) + MkN=ma
a= (mgcos(30)+ MkN)/ m =a

then when I plug in all of the given numbers I get -1.4.
I have tried this problem a bunch of times and cannot get anywhere close to the correct answer. What am I doing wrong?
mostly you've got your mgsin30 and mgcos 30 mixed up.